透明油墨知识简介

在现在的高档包装纸盒上，为了提高包装印刷的效果，经常要提高包装盒的表面亮度，其中普遍的一个做法就是使用特种纸，比如金银卡纸，在这类纸张上面印刷，为了获得更高的光泽度，经常要用到透明油墨来印刷，接下来，笔者讨论一下透明油墨的印刷适性。

透明油墨的特点透明油墨是着色剂全部或大部分采用染料制成的油墨，其遮盖力很低，透明度极高。

1、色相由于透明油墨的透明度很高，印刷后一般都复合镀铝膜，使铝膜的光泽与油墨的光泽相互结合，反射出较为鲜艳的色彩。

而且，采用透明油墨印刷的产品，从不同的角度观看，色相会有较明显的变化，在不同的光源下观察差别会更大一些。

所以，在调配这类油墨时，一定要了解客户复合什么材料，以便按相同的工艺调配油墨，并在相似的环境下观察油墨的色相。

比如有些油墨复合前的色相很接近标准样，但复合后色相可能会相差很远；反之，也有一些油墨印刷后的色相虽然与标准样有一定的差距，但复合后其色相更接近标准样。

透明油墨的色相调配是非常费力的，所以，清楚客户的工艺非常重要。

2、透明度透明油墨的透明度由染料(颜料)和连结料(包含助剂)两部分决定，而且前者起主要作用，后者的影响很小。

就聚氨酯、聚酰胺、氯化聚丙烯这几类常见的树脂制成的油墨而言，聚氨酯油墨的透明度较高。

一般来说，以染料为着色剂的油墨，其透明度比以颜料为着色剂的油墨的透明度要高。

有时由于其他方面的需要，也会在染料中混合使用部分颜料，此时油墨的透明度会有所降低。

3、残留溶剂和异味细心的操作者会发现，透明油墨的干燥速度明显较慢，这是因为透明油墨的固含量低(由于染料比颜料的色浓度高，所以用量无须太多)，溶剂含量高，所以需要对其干燥状况加以控制，否则很容易造成残留溶剂超标，并产生异味。

严重时，复合后溶剂还会慢慢向四周渗透、扩散，使其他颜色发生变色。

所以，在使用此类透明油墨时一定要注意溶剂配比和印刷速度的控制，印刷后再放入40℃左右的熟化室中熟化10多个小时。

4、胶黏剂对透明油墨的溶解透明油墨中所用的染料是完全溶于有机溶剂的，所以当印刷品与复合用胶黏剂发生接触时，胶黏剂中的溶剂就会将印刷品上的透明油墨或多或少地溶解掉。

提高复合速度或者提高胶黏剂的黏度，可以在一定程度上缓解此问题，但也只是治标不治本。

另外，如果透明度允许适当降低，可以在染料中添加部分颜料来制造透明油墨，这对透明油墨的溶解问题也有一定的改善。

此外，针对上述难题，有些油墨厂已经开发出了完全不溶于醇溶性胶黏剂的透明油墨，并在某些印刷材料上得到了很好的应用，相信今后也会开发出不溶于酯溶性胶黏剂的透明油墨。

5、剥离强度透明油墨印刷后的产品在复合镀铝膜时经常发生剥离强度差的问题。

为什么会这样？其实，并不仅仅是透明油墨存在这个问题，当采用其他油墨进行印刷时，如果不印刷白墨衬底，在复合镀铝膜(特别是VMCPP)后也会出现剥离强度差的现象，只不过平时用其他油墨印刷时很少采用这种工艺，所以极少发现剥离强度差的现象。

In today's high-end packaging carton, in order to improve the effect of packaging and printing, often to improve the surface brightness of the box, including the common practice is to use special paper, such as gold and silver cardboard, printed in the type of paper above, in order to obtain higher gloss, often used to print onto the transparent ink Next, we discuss the printability of the transparent ink.Transparent ink characteristicsTransparent ink colorant whole or most of the use made of the ink by the dye, and its opacity is very low, and highly transparent.1 hueDue to the high transparency of transparent ink, printing generally composite aluminized, aluminum gloss and gloss of the ink in combination with each other, reflecting the bright colors. Moreover, the use of transparent ink printed product, as viewed from a different angle, the hue will be more obvious changes observed under different light sources, the difference would be bigger. So, in the deployment of this type of ink, must understand the customer composite what materials, deployment of ink, so that according to the same process and observe the hue of the ink in a similar environment. Example, before some ink composite hue is very close to the standard sample, but composite hue likely will be a difference very far; Conversely, also have some ink printing after the hue Although standard sample have a certain gap, but the composite of its hue is more close to the standard sample. The transparent ink hue deployment is very laborious, and therefore, a clear understanding of the process is very important.2, transparencyTransparency of transparent ink dye (pigment) and links to material (including additives) decision in two parts, and the former plays a major role, the latter has little effect. Polyurethanes, polyamides, chlorinated polypropylene some common resin of the ink, the higher the transparency of the polyurethane ink. In general, the dye is a colorant of the ink, its transparency ratio to the pigment as a coloring agent, and the transparency of the ink must be high. Sometimes because of other needs, will dye mix some paint, ink transparency will decrease.3, the residual solvent and odorCareful operation will be found that the transparent and the ink drying speed is significantly slower, this is because the transparent ink, the low solids content (because the dye is higher than the color of the pigment concentration, the amount need not too much), the solvent content is high,so it is necessary to its dry conditions to control, otherwise it is likely to cause excessive residual solvent and produce odor. Serious, composite after solvent also slowly around penetration, diffusion, other color discoloration. So, when the use of such transparent ink must pay attention to the control of the ratio of solvent and printing speed, printing and then placed in a curing chamber about 40 ℃aging for more than 10 hours.4, adhesives pair of transparent ink, the dissolutionThe dyes used in the transparent ink is completely dissolved in the organic solvent, so when the print and the composite adhesives contact occurs, a solvent in the adhesive is the more or less on a printed transparent ink dissolved out. To improve composite speed or increase the viscosity of the adhesive, you can alleviate this problem to some extent, but only a temporary solution. In addition, if transparency is allowed to be appropriately reduced, can be added in the dye portion pigment to manufacture the transparent ink, which also have a certain improvement in the transparent ink dissolution problem. In response to these problems, some ink factory has developed a completely insoluble in alcohol-soluble adhesive transparent ink, and get some printed material on the application, I believe that will be developed in the future is not soluble in the ester-soluble glue Adhesives transparent ink.5, the peel strengthThe transparent ink after printing products when the composite aluminizer often occurs the problem of poor peel strength. Why is that? In fact, just transparent ink to the existence of this problem, when the using other ink when printing is performed, if not printing white ink substrate, after that the Composite aluminizer (Special is VMCPP) also occur the phenomenon of poor peel strength, but usually with the other ink printing, rarely used in this process, and therefore rarely found the phenomenon of poor peel strength.。